This invention relates to a position controlling unit for controlling a relative position between a recording medium, such as a magnetic disk, and a magnetic head for use in carrying out recording or reading operation, namely, access operation to the recording medium.
A magnetic disk has a central axis and a plurality of concentric tracking axes around the central axis substantially on a recording plane. Each of the tracking axes is for defining a data area. In other words, the data area extends along each of the tracking axes. Various information is recorded in the data area and is accessed by the magnetic head.
In order to access each of the data areas, the magnetic head is movable in a predetermined direction which intersects the tracking axes and extends parallel to the recording plane. Before start of the access operation, the magnetic head is placed on a selected one of the tracking axes. It is necessary for a reliable access operation to exactly control a relative position between the magnetic head and the recording medium.
The magnetic disk has a control area which is indicative of each of the tracking axes. The control area can also be accessed by the magnetic head. Placed on the control area, the magnetic head produces a detection signal. Responsive to the detection signal, the relative position is controlled by a position controlling unit in the manner known in the art.
A conventional position controlling unit is disadvantageous in that it is hard to exactly control the relative position.